【作者】 杜文勇；

【导师】 樊啟洲；

【作者基本信息】 华中农业大学 ， 农业机械化工程， 2007， 硕士

【摘要】 油菜联合收割机脱出物中不仅包含油菜籽粒，而且其大部分为杂物，如长、短茎秆，颖壳，泥沙等。油菜籽的分离与清选是油菜联合收割机的一个重要工作过程。而在油菜联合收割机清选装置中的风速大小和方向对油菜籽的分离与清选起着关键作用。风速过小，会造成矮小杂物及颖壳等一起混杂在油菜籽中；而风速过大，会造成菜籽随杂物一起排出机外，造成损失。因此对清选装置气流场的研究是很有必要和很有意义的。本课题在研究油菜联合收割机脱出物物料特性的基础上，通过运用数值模拟法，利用ANSYS来研究清选装置内气流场的状况。通过试验测定了油菜联合收割机脱出物的物料特性，如油菜籽粒大小、脱出物的悬浮速度等，并得出在含水率相同情况下，脱出物临界悬浮速度有显著差异，油菜籽临界悬浮速度最大，这为清选装置分离原理提供了理论基础和实践。本文以4LZ(Y)——1.5A型油菜联合收割机为研究对象，建立流场的数学物理模型，得出气体流动的控制方程组，在计算域上对流动控制微分方程组进行离散。采用有限元分析软件ANSYS的FLOTRAN模块对内流场进行数值模拟，研究中采用试验所测得的边界条件值，并得出计算域内流速的分布信息。将模拟结果和试验结果进行对比研究，用置信度0.01检验，得到试验值和理论值没有显著差异，说明对其模拟是有效的。利用已建立的模型，对气流场的相关参数进行了研究。通过改变入口风速和入风角，使用该模型计算出了不同组合下清选装置内不同点的流速，并利用SPSS软件进行相关分析。得到入风口速度和入风角对清选装置内气体速度是有影响的(置信度为0.01)，相关系数分别为0.722和0.558，入风口速度对气流场影响较大。同时，利用该模型对本清选装置的参数进行了数值模拟试验。对入风角和风速两个因素分别进行了三个水平及四个水平全排列数值模拟试验。试验结果表明，入风角β=25°，入口风速ν=35m／s时，在所确定的路径上，速度沿y方向的分量较优地满足分离的要求。更多还原

【Abstract】 The thrashed materials in a Rapeseed Combine Harvester contain many things, andmost of them are impurities, such as long and short stern and stalk, hulls mud and sand.The separation and cleaning of rapeseeds is a very important task for a RapeseedCombine Harvester. The strong or weak strength of the wind and the direction of thewind’s entering play a key role in the cleaning and the separation of the rapeseed. If thewind is weak, it will result in some impurities in the seed; if the wind is to strong, it willblow some rapeseeds out of the machine and cause some waste. Therefore, it is highlyimportant and meaningful to do the research on the air flow of the machine. On the basisof the characteristics of the hulls of the Cleaning device of a rapeseed combine harvester,with numerical simulation, the condition of the air current of the selecting machine aremainly studied by using ANSYS in this thesis.According to the experiments, we may know the features of the seed and theimpurities, such as the size of the seed, the impurities’ float speed. The conclusion is thatthe differences among the hulls’ float speed is obvious on the condition that they containthe same moisture content. Comparatively speaking, the rapeseeds’ critical float speed ismuch greater, which gives us the basic theory and practical experiences for the principleof selection device’s separation.The Cleaning Device of a Rape’s Combine Harvester of 4LZ(Y)——1.5A is taken asstudy object, with the aim at building a math-physics model for its air flow, getting theequation about the controlling air current, scattering them via calculating the flowdifferential equation’s limitation. The finite element ANSYS’ FLOTRAN model isapplied to the air current with the purpose of numeric simulation. While on the research,the boundary conditions are got from testing, and the distributing information about thespeed are inferred by calculating in the computation domain. Using the model comparingthe simulated results with the experimented data, under believable degree of 0.01 to, it isfound that there is no evident slight difference between the simulative results and theexperiment result, that is to say, the simulative result is valid.In this thesis the related parameters of the air current is studied by using the builtmodel. Through changing the speed of the wind and the wind’s entering angle, we getdifferent combined group’s flow speed from the calculation under the help of the model.And we use SPSS to analyze some relation ships, among these parameters. And it is found,the wind speed and the wind’s entering angle, have great influence on the cleaning device’s inner flow speed. (The believable degree is 0.01). The correlated coefficients are0.622 and 0.458; the wind speed does have the greater influence. Meanwhile, using thismodel, the numerical simulation is done for the parameters of this machine. A full arrayedtest of numerical simulation is done for the angle of entrance wind with three factors andwind speed with four levels. Test results show that when the angle of the entrance windβ=25°and the wind speed v=35m/s, on the defined path, velocity component along the ydirection can better meet the requirements of separation.更多还原